能解释一下吗?

下面的程序是递归调用的,不是很明白,有谁能解释一下吗?谢谢了
//ruler.cpp -- using recursion to subdivide a ruler
#include <iostream>
const int Len=66;
const int Divs=6;
void subdivide(char ar[],int low,int high,int level);

int main()
{
    char ruler[Len];
    int i;
    for(i=1;i<Len-2;i++)
       ruler[i]=' ';
    ruler[Len-1]='\0';
    int max=Len-2;
    int min=0;
    ruler[min]=ruler[max]='|';
    std::cout<<ruler<<std::endl;
    for(i=1;i<=Divs;i++)
    {
        subdivide(ruler,min,max,i);
        std::cout<<ruler<<std::endl;
        for(int j=1;j<Len-2;j++)
           ruler[j]=' ';
    }
   
    system("pause");
    return 0;
}

void subdivide(char ar[],int low,int high,int level)
{
     if (level==0)
        return;
     int mid=(high+low)/2;
     ar[mid]='|';
     subdivide(ar,low,mid,level-1);
     subdivide(ar,mid,high,level-1);
}